A majority of modern vehicles employ internal combustion engines for propulsion. In search of reduced exhaust emissions, as well as for improved fuel efficiency, some vehicles employ electric motor/generators that combine with an internal combustion engine and a transmission to form a hybrid powertrain. Also for reduced exhaust emissions and improved fuel efficiency, some vehicles incorporate internal combustion engines with stop/start capability.
Stop/start capability allows the engine to be automatically shut off when the vehicle comes to a stop, and to be automatically restarted when the vehicle operator releases the subject vehicle's brake pedal. Generally, stop/start capability reduces the engine's emissions and improves the vehicle's overall fuel efficiency since the engine does not consume fuel or produce post-combustion exhaust when the vehicle is stopped.
As employed in any of the above powertrains, an internal combustion engine is often used to drive an alternator that is configured to produce electric power for running various vehicle accessories and sub-systems, as well as for charging an on-board energy-storage device. In an engine having a stop/start capability, an alternator/motor may be specifically designed to quickly restart an engine that has been shut off, when vehicle motion is again desired.
When such an engine is restarted, it may take time for the subject powertrain to commence transmitting engine torque to the vehicle's drive wheels, thus generating a delay between an instant when a request for vehicle drive is made and when the engine torque is actually applied at the wheels.